Although anti-arrhythmic medications and cardiac pacemakers are used most frequently in the elderly, relatively little attention has been focused on characterizing the patterns of the heart beat in normal elderly subjects over an extended period. In the current project, 104 healthy men and women from the Baltimore Longitudinal Study (BLS) over the age of 60 have undergone ambulatory electrocardiography for a 24-hour period, during part of their regular 2 1/2 day visit to the Gerentology Research Center. A small 2-channel Holter recorder has been employed.